/* kitty: C++ truth table library
 * Copyright (C) 2017-2019  EPFL
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/*!
  \file static_truth_table.hpp
  \brief Implements static_truth_table

  \author Mathias Soeken
*/

#pragma once

#include <array>
#include <cstdint>

#include "detail/constants.hpp"
#include "traits.hpp"

namespace kitty {

/*! Truth table in which number of variables is known at compile time.

  We dispatch on the Boolean template parameter to distinguish between
  a small truth table (up to 6 variables) and a large truth table
  (more than 6 variables).  A small truth table fits into a single
  block and therefore dedicated optimizations are possible.
 */
template <int NumVars, bool = (NumVars <= 6)>
struct static_truth_table;

/*! Truth table (for up to 6 variables) in which number of variables is known at
 * compile time.
 */
template <int NumVars>
struct static_truth_table<NumVars, true> {
    /*! \cond PRIVATE */
    enum { NumBits = uint64_t(1) << NumVars };
    /*! \endcond */

    /*! Constructs a new static truth table instance with the same number of
     * variables. */
    inline static_truth_table<NumVars> construct() const {
        return static_truth_table<NumVars>();
    }

    /*! Returns number of variables.
     */
    inline auto num_vars() const noexcept { return NumVars; }

    /*! Returns number of blocks.
     */
    inline auto num_blocks() const noexcept { return 1; }

    /*! Returns number of bits.
     */
    inline auto num_bits() const noexcept { return NumBits; }

    /*! \brief Begin iterator to bits.
     */
    inline auto begin() noexcept { return &_bits; }

    /*! \brief End iterator to bits.
     */
    inline auto end() noexcept { return (&_bits) + 1; }

    /*! \brief Begin iterator to bits.
     */
    inline auto begin() const noexcept { return &_bits; }

    /*! \brief End iterator to bits.
     */
    inline auto end() const noexcept { return (&_bits) + 1; }

    /*! \brief Reverse begin iterator to bits.
     */
    inline auto rbegin() noexcept { return &_bits; }

    /*! \brief Reverse end iterator to bits.
     */
    inline auto rend() noexcept { return (&_bits) + 1; }

    /*! \brief Constant begin iterator to bits.
     */
    inline auto cbegin() const noexcept { return &_bits; }

    /*! \brief Constant end iterator to bits.
     */
    inline auto cend() const noexcept { return (&_bits) + 1; }

    /*! \brief Constant reverse begin iterator to bits.
     */
    inline auto crbegin() const noexcept { return &_bits; }

    /*! \brief Constant everse end iterator to bits.
     */
    inline auto crend() const noexcept { return (&_bits) + 1; }

    /*! \brief Assign other truth table if number of variables match.

      This replaces the current truth table with another truth table, if `other`
      has the same number of variables.  Otherwise, the truth table is not
      changed.

      \param other Other truth table
    */
    template <class TT, typename = std::enable_if_t<is_truth_table<TT>::value>>
    static_truth_table<NumVars>& operator=(const TT& other) {
        if (other.num_vars() == num_vars()) {
            std::copy(other.begin(), other.end(), begin());
        }

        return *this;
    }

    /*! Masks the number of valid truth table bits.

      If the truth table has less than 6 variables, it may not use all
      the bits.  This operation makes sure to zero out all non-valid
      bits.
    */
    inline void mask_bits() noexcept { _bits &= detail::masks[NumVars]; }

    /*! \cond PRIVATE */
  public: /* fields */
    uint64_t _bits = 0;
    /*! \endcond */
};

/*! Truth table (more than 6 variables) in which number of variables is known at
 * compile time.
 */
template <int NumVars>
struct static_truth_table<NumVars, false> {
    /*! \cond PRIVATE */
    enum { NumBlocks = (NumVars <= 6) ? 1 : (1 << (NumVars - 6)) };

    enum { NumBits = uint64_t(1) << NumVars };
    /*! \endcond */

    /*! Standard constructor.

      The number of variables provided to the truth table must be known
      at runtime.  The number of blocks will be computed as a compile
      time constant.
    */
    static_truth_table() { _bits.fill(0); }

    /*! Constructs a new static truth table instance with the same number of
     * variables. */
    inline static_truth_table<NumVars> construct() const {
        return static_truth_table<NumVars>();
    }

    /*! Returns number of variables.
     */
    inline auto num_vars() const noexcept { return NumVars; }

    /*! Returns number of blocks.
     */
    inline auto num_blocks() const noexcept { return NumBlocks; }

    /*! Returns number of bits.
     */
    inline auto num_bits() const noexcept { return NumBits; }

    /*! \brief Begin iterator to bits.
     */
    inline auto begin() noexcept { return _bits.begin(); }

    /*! \brief End iterator to bits.
     */
    inline auto end() noexcept { return _bits.end(); }

    /*! \brief Begin iterator to bits.
     */
    inline auto begin() const noexcept { return _bits.begin(); }

    /*! \brief End iterator to bits.
     */
    inline auto end() const noexcept { return _bits.end(); }

    /*! \brief Reverse begin iterator to bits.
     */
    inline auto rbegin() noexcept { return _bits.rbegin(); }

    /*! \brief Reverse end iterator to bits.
     */
    inline auto rend() noexcept { return _bits.rend(); }

    /*! \brief Constant begin iterator to bits.
     */
    inline auto cbegin() const noexcept { return _bits.cbegin(); }

    /*! \brief Constant end iterator to bits.
     */
    inline auto cend() const noexcept { return _bits.cend(); }

    /*! \brief Constant reverse begin iterator to bits.
     */
    inline auto crbegin() const noexcept { return _bits.crbegin(); }

    /*! \brief Constant teverse end iterator to bits.
     */
    inline auto crend() const noexcept { return _bits.crend(); }

    /*! \brief Assign other truth table if number of variables match.

      This replaces the current truth table with another truth table, if `other`
      has the same number of variables.  Otherwise, the truth table is not
      changed.

      \param other Other truth table
    */
    template <class TT, typename = std::enable_if_t<is_truth_table<TT>::value>>
    static_truth_table<NumVars>& operator=(const TT& other) {
        if (other.num_vars() == num_vars()) {
            std::copy(other.begin(), other.end(), begin());
        }

        return *this;
    }

    /*! Masks the number of valid truth table bits.

      We know that we will have at least 7 variables in this data
      structure.
    */
    inline void mask_bits() noexcept {}

    /*! \cond PRIVATE */
  public: /* fields */
    std::array<uint64_t, NumBlocks> _bits;
    /*! \endcond */
};

template <int NumVars>
struct is_truth_table<kitty::static_truth_table<NumVars>> : std::true_type {};

} // namespace kitty
